The long-term objective is to understand the effects of parental care, during an early phase of development, on the adult behavior of the offspring. Most such studies have been conducted on mammals and birds, and almost all investigations of sexual imprinting have been on birds, though the conclusions are too freely extended to human beings in the popular literature. Cichlid fishes provide an excellent alternative for testing the generality of such concepts because the monogamous species have well developed bi-parental care of their young. The Midas cichlid offers the further advantage of striking color polymorphism (some fish are gold - G, others normal - N), providing a natural experiment to exploit. In this project, young of G parents are divided into two groups and fostered by parents who are all four possible combinations of two colors and two sexes, as well as no parents. When mature, individual males and females from those five groups are tested to determine the color of mate they prefer. Other experiments will be done on the effects of genetic differences, whether a sensitive period exists, and so on. Cross-fostering has produced the remarkable discovery that the color of the foster parents has a strong effect on the color of the young. N foster parents provide genetically G young with some stimulation that inhibits the loss of melanophores, the process by which N fish become G. Identifying the stimulus, most likely the mucus or skin the young normally eat from the surface of the parents, and the mode of action of the stimulus, may afford a new insight into the metabolism of melanophores, hence a better understanding of the physiology of melanomas. G aggressively dominate N, which enables them to compete more effectively for limiting resources, but enhanced dominance also interferes with G males mating with N females. Demonstrating that early experience with foster parents, which happens through kidnapping in nature, can alter coloration that has such profound social consequences will be a striking example of the indirect effect that early experience can have on behavior through altered morphology.